Author Topic: Why does GPS take you on different routes  (Read 1563 times)

Offline timsatx

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Why does GPS take you on different routes
« on: July 21, 2014, 10:35:28 PM »
For the second time I made a trip out to my daughter in Rosenberg (southwest of Houston) from San Antonio. I didn't pay close attention the first time and it took me on a different route when I left. This time I paid a bit more attention and it took me the same way. I don't know that the second route is shorter but it is at least as fast as there are no stops.

I am just curious as to why it doesn't choose the same route both ways. Next time I will know the roads and make sure I don't turn off and go the direction I don't want to go.

Offline gPink

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Re: Why does GPS take you on different routes
« Reply #1 on: July 22, 2014, 03:49:45 AM »
It's part of your conditioning.

Offline twowheeladdict

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Re: Why does GPS take you on different routes
« Reply #2 on: July 22, 2014, 06:12:46 AM »
right turns versus left turns?

You do have it set on fastest time right?

I almost always check my GPS routes to make sure I agree with what it is trying to do.  Sometimes I have to stick in a Via to avoid going through a town, or section of road I know I don't like.  They are great for what they are, but to blindly follow one when you know orienteering can lead to frustration.
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Offline Rhino

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Re: Why does GPS take you on different routes
« Reply #3 on: July 22, 2014, 06:42:33 AM »
I have a some experience with routing algorithms for connecting integrated circuits. It is a complex problem and small things can effect the solution. One obvious one is one way streets but also the exit from a highway versus the on ramp going the other direction may have different "costs" to the algorithm. Or as 2 wheel said, right versus left turns. In a maze search algorithm, when straight ahead is not a good solution it might first try right instead of left at any given intersection. Giving a different solution for a different direction.

Offline ZG

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Re: Why does GPS take you on different routes
« Reply #4 on: July 22, 2014, 07:23:28 AM »
traffic and/or construction.

Offline Rhino

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Re: Why does GPS take you on different routes
« Reply #5 on: July 22, 2014, 08:02:05 AM »
traffic and/or construction.

True, if your GPS has that function.